1. Field of the Invention
This invention is concerned with presses and more particularly to machines for pressing leather.
2. Prior Art
Hydraulic presses used for smoothing or embossing the surface of leather, comprise upper and lower platens between which the leather is pressed to a predetermined pressure. The upper platen is fixed and the lower platen is vertically movable between a position spaced apart from the upper platen (allowing an operator easy access to a workpiece between the platens), and a position separated from the upper platen only by the thickness of a workpiece between the two platens. Hydraulic cylinders are employed for moving the lower platen towards and away from the upper platen and for applying the required working pressure to the leather workpiece.
Two small diameter hydraulic cylinders and one large diameter hydraulic cylinder are mounted on a base of the aforementioned prior art press. The two small diameter cylinders raise the lower platen from an open condition of the press until a light clamping pressure is exerted on a workpiece between the platens. The large diameter cylinder is pressurized to exert a high load on the lower platen to press the workpiece to the required predetermined pressure. The large diameter cylinder is expensive however, and also needs a large and expensive pre-fill valve to accommodate it, to admit hydraulic fluid under pressure very quickly to the large diameter cylinder, to raise the lower platen at an acceptable speed, and hence, is a drawback associated with the prior art.